In conjunction with a progress of a nanotechnology, the needs of a physical property measurement in a micro region has been enhanced. As a measuring method which can evaluate a structure and a physical property of a material on the basis of a spatial resolving power of nanometer, there can be listed up a measurement of an electric conduction characteristic by a scanning tunneling microscope, an atomic force microscope, a proximity field optical microscope, a transmission electron microscope, a multiple exploratory needle nano probe. In the measurement of the electric conduction characteristic by the multiple exploratory needle nano probe, it is possible to expect such a matter that the information relating to an electron correlation such as a semiconductor device or the like can be obtained, by using four or more exploratory needles.
In a measurement system (hereinafter, refer to as a micro contact type prober) using a multiple exploratory needle nano probe, a short life of the exploratory needle going with a narrow diameter of the exploratory needle and an increase of a contact resistance come into question in future. Particularly, in a failure analysis of a semiconductor device, in order to correspond to a future minute structure of the device, a reservation of a conductivity and an improvement of a mechanical strength in the exploratory needle come to an important factor.
There can be thought that a metal nano wire, a carbon nano tube or the like is applied as the exploratory needle in place of a conventional narrowed metal exploratory needle. For example, in the case of using the carbon nano tube as the exploratory needle, in order to secure a conductivity of the exploratory needle, there is a method of forming a metal film on a surface thereof. In the metal film, it is desirable that it is applied uniformly from a root of the carbon nano tube to a leading end thereof. However, it is not easy to uniformly form the metal film having a good adhesion to a surface of the carbon nano tube.
Under such a background, there have been proposed a method of coating a metal on a surface of a carbon nano tube, and a method of utilizing as a nano probe. As a metal coating method, there is a metal coating method using a pulsed laser deposition (PLD) method, as shown in non-patent document 1. It is a method of irradiating a pulse laser onto a PtIr or W target and depositing a metal on a surface of a carbon nano tube by utilizing a generated plume. It is possible to form a metal film which is extremely thin such as several nm and has a high quality, on the surface of the carbon nano tube in accordance with the PLD method. A resistance value of the exploratory needle can be reduced to 10 kΩ, order in accordance with this method. Further, in patent documents 1 and 2 relating to a prober exploratory needle application of the carbon nano tube, there has been proposed an apparatus which forms a carbon nano tube fixed to a metal exploratory needle in accordance with an electron beam depositing method, cancels a contact resistance on the basis of a four-terminal measurement and measures a micro impedance.
However, in the four-terminal measurement, since a contact resistance value generated with respect to the metal exploratory needle fixing the nano tube, the nano wire or the like, and a resistance value of the nano tube or the nano wire itself becomes higher such as several k to several tens kΩ, there can be thought that it is hard to measure a resistance value of a high resolving power. It is desirable that the contact resistance and the exploratory needle resistance are as low as possible in a substance contact, a wiring and a via resistance measurement, and it is necessary to lower to about 10 Ω, however, in the uniform metal film carbon nano tube exploratory needle disclosed in the patent document 1, since the contact resistance in the leading end is domineering, it has been hard to reduce the resistance to several tens kΩ or less.
The contact resistance coming into question is caused by a small contact stress between the exploratory needle and a measured sample, and an insulating layer such as an oxide film or a contamination of a contact interface.
For example, in the case that the carbon nano tube is set to the exploratory needle, in spite of a very high rigidity such as a Young's modulus of 1 Ta, the carbon nano tube having an aspect ratio equal to or more than 50 is bent sufficiently by a force of several nN. In other words, at a time of applying to the exploratory needle, however the carbon nano tube is pressed, the contact resistance becomes larger since the contact stress is small. Further, since the oxide film and the contamination on the contact interface can be mechanically removed in the conventional metal exploratory needle, however, is bent as mentioned above in the carbon nano tube, a state in which it pinches the oxide film and the contamination is generated, and it is impossible to measure a true resistance value.